This invention relates to a retractable wheel assembly and in particular, although not limited to, a retractable wheel assembly for use with a dinghy or other boat.
Retractable wheel assemblies have a number of design difficulties, mostly relating to the problems of translating a wheel of sufficient size between a compact retracted position and a deployed position quickly, safely and easily while not being visually or physically obtrusive in the retracted position.
Retractable wheel assemblies are of use for a number of purposes and situations. An example of one such use is the attachment of retractable wheel assemblies to the transom of dinghies or other boats, to facilitate movement over land when bringing ashore or launching. Another example is the use of retractable wheel assemblies for retractable luggage wheels. A further example is the use of retractable wheel assemblies to position retractable guides for materials handling.
When used with a dinghy or other boat a number of features would be desirable in the retractable wheel assemblies for the boat to work well on the water and on land.
One such feature is the ability to be able to position the retractable wheel assembly above the line of the hull bottom when retracted so as not to cause drag while the boat is underway in the water.
Another such feature is that the mechanism to deploy the wheel and the wheel itself should be light weight, but strong and rigid when extended to support the weight of the boat.
The wheel should ideally be sufficiently locked in place when in the retracted position so as not to release due to the pounding and vibration of the boat in rough seas when underway.
The wheel should ideally be sufficiently locked in place in the extended position so as to carry the weight of the boat safely when on land.
The retractable wheel assembly should be simple and quick to use by the operator of the boat, when launching from or landing on a shoreline. The operator will often also be operating other equipment such as an outboard motor, sails, or oars when required to retract or extend the wheels; therefore it is advantageous for the retracting and extending mechanisms to be quick and easy to operate preferably by one person and even more preferably using one hand.
Preferably the top of the wheel held by the retractable wheel assembly should not protrude too far above the top of the transom of the boat so as not to restrict the access to or from the boat or impair the normal operation or visually impair the lines of the boat. Yet when the boat is to be used on land, the wheel must be of a suitable size and type to enable easy rolling and adequate ground clearance over a wide variety of surfaces.
A disadvantage of some previous designs has been the height the retractable wheel assembly and wheel has protruded above the top of the transom, hampering normal operation of the boat and visually impairing the boat's lines. One such arrangement is described in U.S. Pat. No. 4,036,507.
Another disadvantage of some previous designs has been the restriction of the type and size of the wheels able to be used due to the design of the mechanism of the retractable wheel assembly thus limiting the type of surface terrain the boat could be easily wheeled over. One such design is described in U.S. Pat. No. 4,588,203.
A further disadvantage of some previous designs has been with locking mechanisms that are difficult to use. A complex design which uses both an over-centre locking mechanism and locking pins is described in U.S. Pat. No. 4,588,203. In this design, a locking pin must be released and transferred between two different apertures and a second locking pin located in a third aperture in order to move the retractable wheel assembly from the locked stowed position to the locked deployed position.
To operate some previous designs with the boat afloat, locking pins must be located in corresponding holes or slots which in some cases are submerged under water. One such design is described in U.S. Pat. No. 4,036,507. To deploy known retractable wheel assemblies with the boat on shore, the retractable wheel mechanism has to be manipulated at the same time as the boat is lifted off the ground; a task often requiring two people to execute safely.